No lights in scene, still lighting up
Objects may appear illuminated, if ...

they are illuminated by lamp objects
they are illuminated by mesh lights with emission shaders
they are emitting light completely or partially, if they have an emission shader
the wrongheaded use of an Add Shader in a material
they are illuminated by the world (background shader)
ambient occlusion is activated

The Ambient Occlusion is activated in your scene.
Uncheck Ambient Occlusion to disable it.
It is found under the World section of the Properties Panel.
Also make sure no light emitting objects are hidden by pressing AltH to unhide all objects.